The present invention relates to the field of paving, and in particular, to a method of simulating the grinding of pavement in order to determine the most effective and efficient means of grinding pavement.
One of the most important measures of the quality of a newly paved road surface is smoothness, that is, the number and size of bumps and dips in the pavement. Smooth roads require less maintenance and conserve fuel. They also provide for a more comfortable ride. Because of the importance of smooth roads, most contractors must adhere to strict specifications concerning the smoothness of the roads they construct. A road which does not meet the specifications may result in the forfeiture of the part of the contract price or may require grinding or filling parts of the pavement, both of which are costly to the contractor. On the other hand, pavement which exceeds specifications for smoothness may result in bonus payments to the contractor. Thus, it is desirable to obtain smoothness data on a newly paved road to determine whether specifications are being met.
Several devices have been utilized for measuring the smoothness or roughness of new pavement construction. One such device is a profilograph, as seen in FIG. 1, which is utilized to create an elevation profile of the road. The profilograph is an elongated beam or frame supported on several wheels. The beam establishes a datum from which deviations in the road surface can be measured. A sensing wheel rolls on a surface and moves vertically as it travels over bumps and dips in the road. The output of a profilograph is a trace profilograph elevation response as a function of distance. Originally, profilographs were entirely mechanical devices which used a linkage to transmit the vertical movement of the sensing wheel to a pen which traced a plot of the road surface on a moving roll of paper. The profilograph plots the elevation of the surface as a function of distance traveled. Typically, a calibrated wheel is used to measure the distance. The roughness was summarized by applying a blanking band and accumulating the height of all protrusions outside the blanking band. The blanking band is effectively a tolerance under which the response is not accumulated. Often, locations for corrective action were simply the location where the blanking band was violated by more than a designated amount. Recently, the blanking band was eliminated in many applications, and proposed locations for grinding were simply the locations where a profilograph response reached a designated level.
Since grinders were built specifically to decrease profilograph response, choosing locations for grinding used in a profilograph was fairly simple. The geometry of a grinder was designed to be similar to a profilograph such that the grinder could follow the profile of the profilograph. Unfortunately, the rating a profilograph gives to pavement features has only marginal relevance to the perception a vehicle driver has when riding on the pavement. This prompted a move to the use of road profiling technology, usually referred to as inertial profilers, as seen in FIG. 2, for evaluation of new construction pavement.
The fundamental difference between profilers and profilographs is that profilographs measure the road with distortion, and profilers measure the road without distortion over the range of wavelengths that affect vehicle vibration response. The distortion of profilograph measurement is determined by its geometry. A trace from a profiler can then be distorted to rate the relevant wavelengths by a computer algorithm. Such computer algorithms allow for the computation of certain roughness indices such as the International Roughness Index (as seen in FIG. 3), Ride Number and Michigan Ride Quality Index.
Measurement of profile and use of a profile-based roughness index is a better way to rate the quality of new pavement, but they are only useful in practice if a method is available to locate and correct the rough spots. For now, pavement bump grinders are the only available tool to correct such rough spots. Because of the bump grinders"" geometry, they do not necessarily improve the values in any of the roughness indices listed above. Therefore, a strategy is needed to guide the proper use of a grinder by choosing locations where grinding provides the best payoff. The economic consideration in the use of this method is the existence of incentive payments for achieving a given smoothness level on new pavement. Typically, state highway agencies that hire pavement contractors include incentive payments for each one-tenth mile-long segment of the new pavement that falls below a given roughness target level. Penalties are occasionally imposed per segment that is rougher than a limit roughness value. In a minority of cases, the incentive bonus structure is based on a graduated roughness scale.
Thus, it would be desirable to provide a quality and cost effective manner in which to correct the roughness of new pavement.
The present invention provides a method for correcting the roughness of pavement. The method includes the steps of measuring an elevation profile of the pavement and converting the elevation profile to a roughness profile. Defective segments are identified as areas of the roughness profile that exceed a predetermined value. A grinding operation is simulated over the defective segments of the roughness profile to create a modified elevation profile. The modified elevation profile is then converted to a modified roughness profile wherein corrected defective segments are identified as those defective segments in the roughness profile that are no longer considered defective segments in the modified roughness profile. The areas of the pavement corresponding to the defective segments are then ground to correct the defective segments in the pavement.